Re: [PATCH v2] ws: add new tab-between-non-ws check

[Junio C Hamano <gitster@pobox.com>]

Adrian Ratiu <adrian.ratiu@collabora.com> writes:

> The check is a bit complex because we want to detect places where
> a SP was intended (HT can expand to more than one display column),
> so we need to count both the display columns (col) and the string
> character columns (i) to determine if a HT looks identical to a SP
> or can cause confusion.
>
> +/....adoc text eol=lf whitespace=trail,space,incomplete,tab-between-non-ws

The name of the whitespace rule does not quite match what we want to
catch.  Can somebody find a phrasing than "between non-ws" that
conveys our intent better?  We want to catch a tab that is used by
mistsake when the writer would have used a space, and "between
non-ws" is one of the heuristics (another is "it is at the 7th
column to make it indistinguishable from a space") the code uses to
tell if a tab is such a mistaken tab.   "tab-instead-of-space"?
"tab-in-place-of-space"?  "tab-that-should-have-been-a-space"?

The last one is horrible and not a serious suggestion, of course.

> +test_expect_success 'check tab between non-whitespace (tab-between-non-ws: off)' '
> +	git config core.whitespace "-tab-between-non-ws" &&
> +
> +	printf "1234567\tb" >x &&

I notice all these printf create incomplete lines.  It is true that
the detection of a tab that is used when it should have been a space
should work even on an incomplete line, but using an incomplete
line, which is of course rather unusual, for these tests gives a
false impression that somehow this requires an incomplete line to
trigger, which is not what we want to give.

	printf "1234567\tb\n" > x &&

or something, perhaps?  I dunno.